The use of hollow fiber bundles as mass transfer devices and energy transfer devices in the field of medical technology is well-known. For example, wound hollow fiber bundles have been used as blood oxygenators and dialyzers. The typical winding pattern for hollow fiber bundles can be described as a helical wind, where the tubes are wrapped around a rotating cylinder. One such winding technique is described in U.S. Pat. No. 4,975,247 by Badolato et al., which describes the means by which to wind a hollow fiber oxygenator with specialized winding equipment. Badolato et al. describes winding a single fiber or fiber ribbon onto a rotating core using a fiber guide which reciprocates along a line parallel to the axis of the core. The fiber guide deposits the tube spirally around the core as the fiber guide reciprocates and the core rotates.
Typical winding techniques such as that described in the Badolato patent are limited to large, for example, 2.0 inch diameter cores. If the core is smaller, the fiber will slide off of the core as the tubing is wound. If the core has a 2.0 inch or larger diameter, contact surface friction will maintain the fiber in place as the fiber is wound. Unfortunately, the relatively large diameter results in a larger priming volume which is undesirable for most medical applications. The increased priming volume results in increased levels of hemodilution which can be deleterious to the patient. In certain instances, the increased priming volume can prohibit the use of the device on smaller adults and children.
Alternatively, hollow fiber bundles may be wound with fiber mats which are not subject to the winding problems of fibers or fiber ribbons, discussed above. Specifically, neither core diameter nor the specific angle at which fibers must be wound around the core to maintain the fiber's position relative to the central axis of the core are factors when using woven fiber mats. As a matter of fact, when a fiber bundle is made using a fiber mat the bundle can be formed around a core with a relatively small diameter and the fibers can be substantially parallel to the axis of the core. However, fiber mats are expensive because of the additional complexities of the weaving process. Further, weaving typically precludes the direct cost control over the manufacturing process that exists when a bundle is wound from a single fiber or fiber ribbon. Therefore, it would be desirable to have a winding technique and apparatus which combines low cost, low prime volume and direct control over production without the disadvantages associated with present winding techniques or wound fiber mat device designs.